85 Chevy suburban K 20

[thecrow71]

I’m doing a project on this vehicle and it has locking rear with 3.42 ratio but I believe it’s semi float which I wanna go to a full float. Is it worth it changing it out to a 10 1/2 full float and also do you have an idea of what the gear ratio is on the front by any chance thank you.

 

[85K304SPD]

Front gear should be the same as the rear. What are you going to use the truck for? Semi floaters are good for most situations.

 

[thecrow71]

Hi, thanks for the reply mainly light 4xing nothing too crazy and road driving. I was just thinking for resale value of somebody else. Wanting to do something a little more hard-core.

 

[thecrow71]

Also, the original sales slip says locking rear with 3.42 ratio

 

[SquareRoot]

A FF in a burb would be a waste of $$ unless your getting it for free and it's a bolt in (not from a c/k 30). An OEM "locking rear" usually means the G80 "Gov Bomb." A reliable aftermarket posi would be more worthwhile than swapping rearends.

 

[thecrow71]

OK thank you yeah I think I’ll just stick with them My only thinking is is I thought the semi floats were only a 9 1/2 inch but this rear one measures 10 1/2 I guess that’s normal and the front axles 9 1/2.

 

[thecrow71]

And one last thing should I keep the 3.42 gears thinking to run and 33’s gonna have a 6.2 L 430 hp LS engine.

 

[Grit dog]

I’d slow down a bit and tackle one question at a time. And learn a bit more about vehicles in general before tearing that burb into 100 pieces.
Basics
All 4wd/AWD have the same front and rear axle ratios unless they’ve been messed with, which is up to you to figure out. Although it seems your question came from a lack of fundamental knowledge, not suspicion that one axle had been switched to a different gear ratio. We can’t “see” your truck but it’s real easy to verify gear ratio in axles manually. You should do that if you’re suspicious it’s been swapped with a non matching set of gears.

FF vs semi isn’t going to “add value” inherently. The other 99% of the truck will determine its value, especially in a burb which would under 99% of circumstances never need the extra capacity of a FF axle. Best case you’ll spend far more time and $ swapping rear axles if there ls nothing wrong with yours than you’ll recoup hypothetically down the figurative road.
Gear ratios. The basics. You didn’t say what transmission. And it’s one of the 3 or 4 big factors in determining the best final ratio.
Namely are you using an OD trans? Double OD? Triple OD? What OD ratios? Any 6.2 half ton truck engine came in front of a 6,8 or 10 speed.
Or are you buying a crate motor? ($$$$)

On a separate note, if you’re talking about added resale value, I’m presuming this isn’t an emotional “keep it forever” build. And presuming you’re building/finishing the rest of the vehicle to be commensurate with a hotrod LS swap and talkin FF bombproof axle, it’s gonna take a lot of money to do that.
From a resale standpoint, burbs are only worth a fraction of the closest corresponding pickup truck, across the board. Just food for thought…

Short story is yes 3.42s are about ideal for 33s if you have a 1:1 top gear trans. Maybe 3.73s. The LS will handle any rpm’s you want to run, but will your wallet and ears? And do you want something that will purr along at 90mph on the freeway or be running high rpm’s.
You can use any of the multitude of online gear ratio rpm calculators to decide.

 

[thecrow71]

Yes, no I admit I am a novice when it comes to certain things I know what I know and don’t know what I don’t know that’s why I came here and it’s SM 465 transmission. Thanks for your time and input. I’m gonna do what you’re saying and not worry about that and leave what’s well enough alone. And yes, crate engine from summit racing. Thanks again.

 

[Big Ray]

85...i bet it has 14 bolt.
If it's not the 10.5" full floater it's a 9.5" semi floater.
There's absolutely nothing wrong with the 9.5" 14 bolt.
Unless you're going rock bouncing or something like that.
I prefer it myself.

 

[DoubleDingo]

Run the semi-float. Fix everything else that needs fixin, and run it as-is. If it has the g80, don't explode it.

 

[Big Ray]

The 14 bolt g80 will be stronger than the 10 bolt g80 due to the parts being larger.

 

[Frankenchevy]

Another consideration if you do still want to start swapping axles…14ff is probably more likely to have a 3.73 or lower (higher numerically, ie 4.10) which will add a significant cost to regear so axle ratios match, and you’ll want to find something from a 3/4 ton unless you want to cut off spring perches and reweld. 1 tons have different spring spacing.

 

[SquareRoot]

The 14 bolt g80 will be stronger than the 10 bolt g80 due to the parts being larger.

But.....larger parts mean a larger BANG! lol